It is known that Biolimus A9, a rapamycin derivative, is an immunosuppressant, and is also proven to have anti-tumor and anti-fungal effect.
Several prior arts had disclosed the improvements of the product yield of rapamycin derivatives. U.S. Pat. No. 7,193,078 to Isozaki et al. disclosed a process for producing Biolimus A9, giving an example to obtain a yield of 46% by reacting rapamycin with 2-ethoxyethyl trifluoromethane sulfonate (or 2-ethoxyethyl triflate) in an organic solvent.
However, the Isozaki's prior art still has the following drawbacks:    1. Even one example ever showed a 46% yield of Biolimus A9, it however just revealed a small-scale laboratory experiment with only one gram (1.09 mmol) of rapamycin and 1.95g (8.78 mmol) of 2-ethoxyethyl triflate. After amplifying or expanding the process to be larger scale, the yield will be remarkably reduced to thereby decrease the commercial or industrial value of this prior art (Note: The low yield after simulated process amplification will be hereinafter discussed in Examples 3, 4 of this application).    2. Even the reactant of 2-ethoxyethyl triflate is a compound with high activity, it is unstable and will be decomposed such as after being stored for one week at room temperature. Also, the triflate is not UV-absorbable and is therefore unsuitable for process tracking when proceeding the reaction. Such poor properties will affect the material storage, production scheduling and process tracking for commercially making the Biolimus A9.
The present inventor has found the drawbacks of the prior art and invented the present process for making Biolimus A9 efficiently and economically.